TWI828921B - Rubber moldings and battery packs - Google Patents

Abstract

The present invention is a rubber molded body that is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole to cover at least the safety valve or the vent hole. According to JIS H7903:2008, utilizing The thermal conductivity (measurement temperature: 33°C) measured by the one-way heat flow steady-state comparison method does not reach 1.0 W/m・K, and the thickness of the part covering the above safety valve or the above exhaust hole is 0.3 mm or more and 10.0 mm or less, based on JIS K6253, the surface hardness measured using a type A hardness tester is between 50 and below 90.

Description

Rubber moldings and battery packs

The present invention relates to a rubber molded body formed by molding and hardening a rubber composition, and a battery pack including a lithium ion secondary battery cell equipped with the rubber molded body.

In recent years, demand for lithium-ion secondary batteries (hereinafter sometimes also referred to as "batteries") has increased. On the other hand, with the development of miniaturization and high energy density (energy density is 300 Wh/kg or more), there are risks such as heat generation and high temperature depending on the use method. Therefore, the safety of the battery or battery pack becomes more important.

For example, if a lithium-ion secondary battery is overcharged or overdischarged, or is accidentally impacted and causes an internal or external short circuit, there is a risk of thermal runaway. A lithium-ion secondary battery that experiences thermal runaway will produce gas and increase the internal pressure of the battery. If this happens, the internal pressure may rise, causing the packaging can to rupture, etc. Therefore, these batteries are equipped with vents or safety valves for exhaust.

In addition, when thermal runaway occurs, there is a risk of ignition caused by an overheated battery, etc. In order to prevent spread and burning, for example, in Patent Document 1, the surface of the battery is covered with a fireproof sheet.

However, high-temperature and high-pressure gases will be ejected from the exhaust holes or safety valves provided for exhausting the lithium-ion secondary batteries that have experienced thermal runaway. According to the description of Non-Patent Document 1, even for a moment, the maximum temperature may exceed 999°C.

Therefore, the fireproof sheet of Patent Document 1 is provided to prevent flames originating from the high-temperature gas (that is, to prevent fire). [Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2019-032923 [Non-patent literature]

[Non-patent document 1] Hideki Matsumura, Kazuo Matsushima Summary of speech at the Forum of the Institute of Traffic Safety and Environment / Editor of the Institute of Traffic Safety and Environment 135-138, 2012

[Problem to be solved by the invention]

However, due to the high energy density of batteries in recent years, the pressure of gas discharged during thermal runaway has increased significantly. Due to the high pressure of the gas, there is a risk of damage even to the fireproof sheet of Patent Document 1. Specifically, for example, in the case of the fireproof sheet made of fibers described in Patent Document 1, the high pressure of the gas causes the mesh of the fibers to expand, and in the case of the fireproof sheet made of resin, , in the softened state of the resin before reaching the burning state, the fireproof sheet is reduced to a strength that cannot withstand high pressure and burns through. Therefore, no matter what the situation, there is the following risk: the fireproof sheet will produce through holes and eject from the through holes. The high-temperature, high-pressure gas spreads to components other than the fire-proof sheet (such as the packaging shell that contains the battery) and burns it, and finally spreads to the machines and vehicles equipped with the battery and burns them.

In addition, there is a risk that air (oxygen) is supplied from the through hole, causing the battery itself to burn and spread, causing thermal runaway of an adjacent normal lithium-ion secondary battery.

The present invention was made in view of the above background, and its object is to provide a rubber molded body and a battery pack including a lithium ion secondary battery cell equipped with the rubber molded body, even if the lithium ion secondary battery is thermally runaway. When high-temperature and high-pressure gas is ejected from the safety valve or exhaust hole of the lithium-ion secondary battery, the rubber molded body can also prevent the spread or burning of the gas. [Technical means to solve the problem]

In order to achieve the above object, the present invention is constituted as follows.

(1) The rubber molded body of the present invention is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole to cover at least the safety valve or the vent hole. According to JIS H7903:2008, use The thermal conductivity (measurement temperature: 33°C) measured by the one-way heat flow steady-state comparison method does not reach 1.0 W/m・K, and the thickness of the part covering the above safety valve or the above exhaust hole is 0.3 mm or more and 10.0 mm or less, based on JIS K6253, the surface hardness measured using a type A hardness tester is between 50 and below 90.

According to the present invention, a rubber molded body with thermal conductivity, thickness, and surface hardness within a specific range is attached to cover the safety valve or vent hole of the lithium ion secondary battery cell. Therefore, even if the lithium ion secondary battery generates heat, If there is no control, the rubber molded body will not have through-holes caused by the high-temperature and high-pressure gas ejected from the safety valve or exhaust hole, thereby suppressing the spread of burning and burning caused by the ejection of high-temperature and high-pressure gas.

(2) The rubber molded body of the present invention is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole to cover at least the safety valve or the vent hole. The rubber molding system uses silicone A rubber composition formed by molding and hardening. The silicone rubber composition contains 10 to 100 parts by mass of powdered silicon dioxide and 10 to 50 parts by mass of powdered silicon dioxide based on 100 parts by mass of organopolysiloxane. Layered silicate, not less than 0.5 parts by mass and not more than 20 parts by mass of titanium oxide, and not less than 4.0 parts by mass and not more than 14.0 parts by mass of hardener. According to the present invention, a rubber molded body formed by molding and hardening a silicone rubber composition of a specific component is attached to cover the safety valve or vent hole of the lithium ion secondary battery cell. Therefore, even if the lithium ion secondary battery is damaged, Thermal runaway can also prevent the rubber molded body from forming through holes due to high-temperature and high-pressure gas ejected from the safety valve or exhaust hole, thereby suppressing burning and burning caused by the ejection of high-temperature and high-pressure gas.

(3) The rubber molded body of the present invention is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole to cover at least the safety valve or the vent hole. The rubber molding system uses silicone A rubber composition formed by molding and hardening. The silicone rubber composition contains 10 to 100 parts by mass of powdered silicon dioxide and 10 to 50 parts by mass of powdered silicon dioxide based on 100 parts by mass of organopolysiloxane. Layered silicate, not less than 0.5 parts by mass but not more than 20 parts by mass of titanium oxide, not less than 4.0 parts by mass and not more than 14.0 parts by mass of hardener, According to JIS H7903:2008, the thermal conductivity of this rubber molded body measured using the one-way heat flow steady-state comparison method (measurement temperature: 33°C) is less than 1.0 W/m・K. This rubber molded body covers the above-mentioned safety valve or the above-mentioned exhaust valve. The thickness of the pore portion is 0.3 mm or more and 10.0 mm or less. The surface hardness of the rubber molded article measured using a type A hardness tester is 50 or more and 90 or less based on JIS K6253. According to the present invention, a rubber molded body is attached to cover the safety valve or vent hole of the lithium ion secondary battery cell. The rubber molding system is formed by molding and hardening a silicone rubber composition of a specific component, and has high thermal conductivity, thickness , and the surface hardness is within a specific range. Therefore, even if the lithium-ion secondary battery undergoes thermal runaway, the rubber molded body will not have through holes due to the high-temperature and high-pressure gas ejected from the safety valve or exhaust hole, thereby suppressing the occurrence of high-temperature and high-pressure gases. , Spreading and burning caused by the ejection of high-pressure gas.

(4) In a preferred embodiment of the rubber molded article of the present invention, the rubber molded article has an elongation at the time of cutting of 80% or more and 500% or less. According to this embodiment, when attaching the rubber molded body to the lithium ion secondary battery cell, it is easy to apply tension in such a manner that the rubber molded body is in close contact with the safety valve or vent hole of the lithium ion secondary battery cell, and at the same time, the safety valve is covered Or a rubber molded body is attached to maintain the thickness of the vent hole at a required thickness.

(5) In another embodiment of the rubber molded article of the present invention, the rubber molded article is in the shape of a sheet, a belt, or a cap. According to this embodiment, when the rubber molded body is attached to the outer periphery of the lithium ion secondary battery cell to cover the safety valve or the exhaust hole, it can be attached in a preferred form corresponding to the shape of the rubber molded body.

(6) The battery pack of the present invention includes one or more lithium ion secondary battery cells with the rubber molded body according to any one of (1) to (5) attached to the outer periphery. According to the present invention, a rubber molded body is attached to the outer periphery of the lithium ion secondary battery cell to cover the safety valve or vent hole. Therefore, even if the lithium ion secondary battery undergoes thermal runaway, the rubber molded body will not be affected by the thermal runaway. The high-temperature and high-pressure gas ejected from the safety valve or the exhaust hole creates through holes, thereby preventing the ejection of high-temperature and high-pressure gas from spreading to the battery pack or burning the battery pack.

(7) In a preferred embodiment of the present invention, at least part of the outer peripheral surface of the lithium ion secondary battery cell is covered with a putty-like composition having thermal conductivity. The thermal conductivity (W/m·K) of the putty-like composition is preferably 1.5 or more and 16.0 or less. According to this embodiment, at least part of the outer peripheral surface of the lithium ion secondary battery cell is covered with a thermally conductive putty-like composition. Therefore, even if the lithium ion secondary battery generates heat due to thermal runaway, the heat can be efficiently dissipated. It is released outside the lithium ion secondary battery cell, thereby inhibiting overheating of the lithium ion secondary battery cell. [Effects of the invention]

As described above, according to the present invention, the rubber molded body is attached to cover the safety valve or the vent hole of the lithium ion secondary battery cell. Therefore, even if the lithium ion secondary battery undergoes thermal runaway, the rubber molded body will not be damaged due to thermal runaway. The high-temperature and high-pressure gas ejected from the safety valve or exhaust hole creates through-holes, thereby suppressing the spread and burning caused by the ejection of high-temperature and high-pressure gas.

Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1 is a perspective view of a lithium ion secondary battery cell equipped with a rubber molded body according to an embodiment of the present invention.

The lithium ion secondary battery cell 1 is a square battery cell. A positive terminal 3 and a negative terminal 4 are provided on the upper surface of a packaging can 2 which is a battery container, and a safety valve 5 is provided therebetween.

When the lithium-ion secondary battery cell 1 undergoes thermal runaway and the internal pressure rises, the safety valve 5 is activated to prevent the packaging can 2 from rupturing due to the ejection of high-temperature and high-pressure gas.

When thermal runaway occurs in the lithium-ion secondary battery cell 1, there is a risk of catching fire due to overheating. If the high-temperature and high-pressure gas ejected from the safety valve 5 spreads over a wide area at once, it will be difficult to prevent spread and burning.

Therefore, in this embodiment, as shown in FIG. 2, FIG. 3, and the cross-sectional view along line A-A of FIG. 3, that is, FIG. In this way, a flexible sheet-like rubber molded body 6 is attached.

In this embodiment, the insulating sheet 7 and the sheet-like rubber molded body 6 are both rectangular and have approximately the same size, so as to cover the upper surface of the rectangular parallelepiped lithium ion secondary battery cell 1 including the safety valve 5 and cover the front and back sides (Fig. 4 Attached to the upper part of the left and right sides).

Lead wires (not shown) connected to the positive terminal 3 and the negative terminal 4 of the lithium ion secondary battery cell 1 are drawn out from the side that is not covered by the insulating sheet 7 and the rubber molded body 6 .

The lithium ion secondary battery cell 1 with the insulating sheet 7 and the sheet-shaped rubber molded body 6 is stored in a packaging case (not shown). In the packaging case, the rubber molded body 6 covering the front and back upper portions of the lithium ion secondary battery cell 1 is pressed by the inner wall of the packaging case, thereby holding the rubber molded body 6 .

The rubber molded body 6 of this embodiment is formed by molding and hardening the following rubber composition. The thermal conductivity of the rubber molded body 6 is measured using the one-way heat flow steady-state comparison method (SCHF) in accordance with JIS H7903:2008. Temperature: 33℃) does not reach 1.0 W/m・K.

If the thermal conductivity is 1.0 W/m·K or more, when the lithium-ion secondary battery undergoes thermal runaway, heat will be conducted through the rubber molded body due to the high-temperature and high-pressure gas ejected from the safety valve or exhaust hole. The outer peripheral member of the rubber molded body 6, such as a packaging case for housing the lithium ion secondary battery cell 1 covered with the sheet-like rubber molded body 6, melts and deforms the packaging case.

The lower the thermal conductivity, the better, and its lower limit is, for example, 0.1 W/m・K.

Furthermore, regarding the thickness of the portion of the rubber molded body 6 covering the safety valve 5, in this embodiment, the rubber molded body 6 is in the form of a sheet with a uniform thickness, and the thickness of the sheet-like rubber molded body 6 is preferably 0.3 mm or more and 10.0 mm. or less, more preferably not less than 0.5 mm and not more than 5 mm, still more preferably not less than 0.7 mm and not more than 2 mm.

If the thickness is less than 0.3 mm, the high-temperature and high-pressure gas ejected from the safety valve 5 will cause a through hole in the rubber molded body 6, and the high-temperature and high-pressure gas will be ejected from the through hole and spread to the insulating sheet 7 and the sheet. The lithium ion secondary battery cell 1 covered by the rubber molded body 6 is burned by the outer components. In addition, the through hole serves as a supply port for air (oxygen), thereby spreading and burning the lithium ion secondary battery cell 1 itself covered with the insulating sheet 7 and the sheet-like rubber molded body 6 .

If the thickness of the sheet-shaped rubber molded body 6 exceeds 10.0 mm, high-temperature and high-pressure gases can be blocked, that is, no through holes are generated, but the rubber molded body 6 becomes larger and the molding process becomes complicated. Furthermore, it is difficult to store the lithium ion secondary battery cell 1 in an existing packaging case.

The surface hardness of the rubber molded body 6 is measured using a type A durometer based on JIS K6253, and is preferably 50 or more and 90 or less. If the surface hardness is less than 50, the rubber molded body 6 will be damaged or have through holes due to the influence of high-temperature and high-pressure gas ejected from the safety valve 5 (especially the influence of pressure (ejection force)). If the surface hardness exceeds 90, it will become brittle. Therefore, when the sheet-shaped rubber molded body 6 is attached to the lithium ion secondary battery cell 1 in a manner to impart curvature, or when it is exposed to high-temperature or high-pressure gas ejected from the safety valve 5, etc. Will break in case of accidental impact.

The rubber molded body 6 is not limited to the following rubber composition, as long as it is formed by molding and hardening the rubber composition. The rubber molded body 6 will not burn through or generate heat due to the heat of high-temperature and high-pressure gases like resin molded bodies. Through holes, therefore preferred.

The rubber molded article 6 of this embodiment is formed by molding and hardening a rubber composition whose main component is a silicone rubber composition.

The silicone rubber composition suitable for the rubber molded article 6 contains 10 to 100 parts by mass of powdered silicon dioxide and 10 to 50 parts by mass of layered silicon dioxide, respectively, based on 100 parts by mass of organopolysiloxane. Silicate, 0.5 to 20 parts by mass of titanium oxide, 4.0 to 14.0 parts by mass of hardener.

The organopolysiloxane is, for example, represented by the average unit formula: RaSiO(4-a)/2 (in the formula, R is a hydrocarbon group or a halogenated alkyl group; a is 1.95 or more and 2.05 or less). Examples of the hydrocarbon group R include: alkyl groups such as methyl, ethyl, and propyl; alkenyl groups such as vinyl and allyl; cycloalkyl groups such as cyclohexyl; aralkyl groups such as β-phenylethyl; and phenyl groups. , tolyl and other aryl groups, etc. Examples of R of the halogenated alkyl group include 3,3,3-trifluoropropyl, 3-chloropropyl, and the like. Regarding organopolysiloxane, it is preferable to use an organic peroxide and/or a platinum-based catalyst as a hardener to cross-link the molecules at the positions of the hydrogen atoms bonded to the silicon atoms in the molecules. It has at least 2 alkenyl groups bonded to silicon atoms in the molecule. Examples of the alkenyl group include vinyl, allyl, propenyl, hexenyl, and the like. The molecules of organopolysiloxane can be linear or branched.

Examples of powdered silica include dry process silica such as fumed silica and wet process silica such as precipitated silica. Furthermore, examples of powdered silica include: dry process silica or wet process silica whose surface is coated with organochlorosilanes, organoalkoxysilanes, hexaorganodisilazane, and organosiloxane oligomers. Materials, etc. that undergo hydrophobization treatment. Powdered silica preferably contains one or more of these to improve the sinterability. Even if the lithium ion secondary battery undergoes thermal runaway and high-temperature and high-pressure gas is ejected from the safety valve, the rubber molded body will not penetrate. From the viewpoint of forming pores and maintaining shape, it is more preferable to include hydrophobized dry-process silica.

The specific surface area of powdered silica measured by the multi-point nitrogen adsorption method (BET method) of JISK6430:2008 is preferably 50 m ² /g or more. The primary median particle size of the powdered silica measured using a laser diffraction/scattering particle size distribution measuring device is preferably 1 μm or more and 10 μm or less. From the viewpoint of fire resistance, the content of powdered silicon dioxide in the silicone rubber composition is preferably from 10 parts by mass to 100 parts by mass relative to 100 parts by mass of the organopolysiloxane. If it is less than 10 parts by mass , then the high-temperature and high-pressure gas ejected from the safety valve 5 creates a through hole in the rubber molded body 6 . If it exceeds 100 parts by mass, the surface hardness of the rubber molded body 6 increases and becomes brittle.

Examples of the layered silicate include mica, montmorillonite, bentonite, illite, sepiolite, allervardites, magnesium chlorite, lithium bentonite, talc, fluorolithium bentonite, saponite, and aluminum silicate. Stone, nontronite, sillimanite, bentonite, vermiculite, fluvermiculite, halloysite, etc. The layered silicate preferably contains one or more of these, and more preferably contains mica from the viewpoint of improving sintering properties and maintaining the stability of the lithium ion secondary battery. Examples of mica include muscovite, biotite, phlogopite, and the like. The median particle diameter of the layered silicate measured using a laser diffraction/scattering particle size distribution measuring device is preferably 1 μm or more and 100 μm or less. The median particle size of the layered silicate is preferably larger than the primary median particle size of the powdered silica. From the perspective of improving the sintering properties, even if the lithium ion secondary battery undergoes thermal runaway and high-temperature and high-pressure gas is ejected from the safety valve 5, through holes will not be formed in the rubber molded body 6. In terms of fire resistance, silicone The content of the layered silicate in the rubber composition is preferably 10 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the organopolysiloxane.

Furthermore, from the viewpoint of maintaining the shape of the rubber molded body 6 (maintaining the shape even when exposed to high temperatures), the content of the layered silicate in the silicone rubber composition is preferably greater than the content of powdered silica.

The silicone rubber composition contains titanium oxide as a heat resistance improving agent. The blending amount of titanium oxide is preferably in the range of 0.5 to 20 parts by mass based on 100 parts by mass of the organopolysiloxane, more preferably 1.0 to 10.0 parts by mass. If the blending amount is less than 0.5 parts by mass, the heat resistance of the rubber molded body 6 will be insufficient. If it exceeds 20.0 parts by mass, the flame retardancy of the rubber molded body 6 will decrease.

In addition to titanium oxide, metal oxides such as iron oxide, silicon dioxide, and zinc oxide may be used together, and graphite, aluminum, etc. may be used together with the metal oxides as heat resistance improving agents.

The silicone rubber composition needs to be hardened to a desired hardness, so it contains 4.0 to 14.0 parts by mass of a hardener with respect to 100 parts by mass of organopolysiloxane. If it is 4.0 parts by mass or less, the surface hardness of the rubber molded body 6 is insufficient and, for example, it is easily damaged when attached to the outer periphery of the lithium ion secondary battery cell 1 . If it exceeds 14.0 parts by mass, the rubber molded body 6 will become brittle.

As the hardener, organic peroxide or platinum-based catalyst is preferred.

The rubber molded body 6 can be manufactured by applying a known manufacturing method.

For example, the above materials can be mixed and kneaded, extruded into a sheet with a desired thickness, and subjected to primary vulcanization (conditions: below 120°C, 10 minutes) and secondary vulcanization (conditions: 200°C, 4 hours). Make. The sheet-shaped product may be cut into a specific width and formed into a belt shape. In addition, it can also be injection molded or press molded into a desired shape, and then primary vulcanization and secondary vulcanization can be performed to harden it.

If the elongation of the rubber molded body 6 when cut is 80% or more and 500% or less, the rubber molded body 6 is attached to the outer periphery of the lithium ion secondary battery cell 1 while applying tension when attaching it to cover the safety valve 5 It is preferable in terms of the aspect, and more preferably the elongation at the time of cutting is not less than 100% and not more than 350%.

If the elongation at the time of cutting is less than 80%, the rubber molded body 6 will tend to break when attached to cover the safety valve 5. If the elongation at the time of cutting exceeds 500%, the thickness of the rubber molded body 6 will change. Thin, it is easy to produce through holes due to the ejection of high-temperature and high-pressure gas.

As described above, in this embodiment, the rubber molded body 6 is attached to cover the safety valve 5 of the lithium ion secondary battery cell 1. Therefore, even if the lithium ion secondary battery undergoes thermal runaway, the rubber molded body 6 will not The through-hole is created by the high-temperature and high-pressure gas ejected from the safety valve 5, thereby suppressing the spread of burning and burning caused by the ejection of high-temperature and high-pressure gas.

In the above-described embodiment, the insulating sheet 7 and the rubber molded body 6 that are attached to cover the upper surface of the lithium ion secondary battery cell 1 and cover the upper parts of the front and back surfaces cover the lithium battery when stored in the packaging case as described above. The rubber molded bodies 6 on the front and back of the ion secondary battery cell 1 are pressed by the inner wall of the packaging case, thereby holding the rubber molded bodies 6 .

On the other hand, in another embodiment of the present invention, as shown in FIG. 5 corresponding to the above-mentioned FIG. 3, the rubber molded body 6 can also be fixed to the packaging can of the lithium ion secondary battery cell 1 through the adhesive tape 8. 2. In FIG. 5 , the adhesive is formed across the front and rear ends of the sheet-shaped rubber molded body 6 covering the lithium ion secondary battery cell 1 and the packaging can 2 of the lithium ion secondary battery cell 1 . The rubber molded body 6 is fixed to the lithium ion secondary battery cell 1 by winding the tape 8 and attaching it.

Thereby, the positional deviation of the insulating sheet 7 and the rubber molded body 6 covering the lithium ion secondary battery cell 1 can be suppressed.

Furthermore, when the insulating sheet 7 and the rubber molded body 6 are attached to the lithium ion secondary battery cell 1, tension can be applied so that the gap between the upper surface of the lithium ion secondary battery cell 1 and the insulating sheet 7 becomes smaller. Fix with adhesive tape 8.

Thereby, the insulating sheet 7 and the rubber molded body 6 can be in close contact with the safety valve 5 on the upper surface of the lithium-ion secondary battery cell 1, thereby effectively suppressing the thermal runaway of the lithium-ion secondary battery and ejection from the safety valve 5. High-temperature, high-pressure gas diffuses all at once.

Furthermore, since the rubber molded body 6 has rubber elasticity, even if high-pressure gas is suddenly ejected from the safety valve 5, the pressure can be relaxed by expansion.

As the adhesive tape 8, a polyimide film coated with an acrylic adhesive, a silicone adhesive, etc. can be used. Among them, an adhesive tape with a polyimide film coated with a silicone adhesive is heat-resistant. It has excellent properties, so it is better.

FIG. 6 is a perspective view corresponding to FIG. 3 of another embodiment of the present invention, and FIG. 7 is a cross-sectional view along line B-B of FIG. 6 .

In this embodiment, the entire outer peripheral surface of the lithium ion secondary battery cell 1 is covered with a putty-like composition 9 having excellent thermal conductivity.

The insulating sheet 7 and the sheet-like rubber molded body 6 are attached through the putty-like composition 9 so as to cover the upper surface, the upper part of the front surface, and the lower part of the back surface of the lithium ion secondary battery cell 1 .

By coating the outer peripheral surface of the lithium ion secondary battery cell 1 with the putty-like composition 9 having excellent thermal conductivity in this manner, even if the lithium ion secondary battery cell 1 generates heat due to thermal runaway, the heat can be efficiently conducted. to the outside of the lithium ion secondary battery cell 1 to dissipate heat and make the overall heat distribution uniform.

Since the putty-like composition 9 can be coated to follow the surface shape of the member to be coated, that is, the lithium ion secondary battery cell 1, it can increase the contact area with the lithium ion secondary battery cell 1 as a heat source, thereby significantly improving the Heat dissipation.

The thickness of the coated putty-like composition 9 is preferably 2 mm or more and 5 mm or less.

The area covered with the putty-like composition 9 may be the entire outer peripheral surface of the lithium ion secondary battery cell 1 as in this embodiment, or may be a part thereof. Preferably, it is directly above the safety valve 5 of the lithium ion secondary battery cell 1 .

That is, it is preferable that the layer of the putty-like composition 9 excellent in thermal conductivity and the rubber molded body 6 are laminated directly above the safety valve 5 of the lithium ion secondary battery cell 1 .

As the putty-like composition excellent in thermal conductivity, the following compositions (1) and (2) are preferred.

(1) A composition containing a liquid polymer, aluminum hydroxide, and bentonite, the content of the aluminum hydroxide being 150 to 1000 parts by mass relative to 100 parts by mass of the liquid polymer, and the above The content of bentonite is 5 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the liquid polymer.

(2) A composition, which is a thermally conductive putty composition containing a base polymer and a thermally conductive filler. The base polymer contains a liquid polymer having a hydroxyl group as a main component, and the content of the thermally conductive filler is relative to the base polymer. 100 parts by mass means not less than 500 parts by mass but not more than 3,000 parts by mass.

Here, "putty-like" means that the penetration amount (measurement temperature: 23±3°C) measured in accordance with JIS A5752:1994 is 50 mm or more and 160 mm or less.

In addition, the so-called "liquid polymer" refers to a polymer that is liquid at normal temperature and normal pressure (25°C, 1 atmosphere). Examples of the liquid polymer include liquid polyolefins such as liquid polybutadiene, liquid polyisoprene, liquid polybutene, and liquid ethylene-propylene copolymer; liquid silicone; liquid silicone; Acrylic acid; liquid urethane, etc. The liquid polymer preferably contains one or more of these, and more preferably contains liquid polyolefin. From the viewpoint of preventing the generation of halogen gas during combustion, the liquid polymer preferably does not contain halogen elements in its molecules.

The characteristics of the putty-like composition with excellent thermal conductivity in (1) above are: (A) Thermal conductivity (W/m・K): 1.5 or more and 3.5 or less (B) Softness (penetration mm): 50 or more and 110 or less.

The characteristics of the putty-like composition with excellent thermal conductivity in (2) above are: (A) Thermal conductivity (W/m・K): 5.0 or more and 16.0 or less (B) Softness (penetration mm): 60 or more and 160 or less.

If we look at the heat dissipation performance (A) × (B) taking into account shape following properties, Then the heat dissipation performance of the above (1) is above 150 and below 314, The heat dissipation performance of the above (2) is above 390 and below 1036.

As one of the reasons why the heat dissipation performance of the above (2) is better than that of the above (1), it is speculated that the reason is that it has a hydroxyl group.

Each of the above embodiments is applied to one lithium ion secondary battery cell 1 , but the present invention can of course be applied to a plurality of lithium ion secondary battery cells 1 .

For example, as shown in FIGS. 8 and 9 corresponding to the above-mentioned FIGS. 2 and 3 respectively, a plurality of lithium-ion secondary battery cells 1 , in this example four, may be connected to a busbar (not shown). Battery pack, for this battery pack, insulating sheets 7 and Sheet-shaped rubber molded body 6.

The four lithium ion secondary battery cells 1 with the insulating sheet 7 and the rubber molded body 6 attached in this manner are housed in a packaging case 10 made of, for example, resin as shown in FIG. 10 to form a battery pack 11 . (Another embodiment)

In the above embodiment, the rubber molding system is configured to cover the upper surface of the lithium ion secondary battery cell and the upper parts of the front and back surfaces, but it may also cover substantially the entire surface except for the lead portion of the lithium ion secondary battery cell. way of composition. In this case, the packaging shell can be omitted.

In each of the above embodiments, the rubber molded body is in the form of a sheet, but it is not limited to a sheet shape. It suffices as long as it has a shape that can at least cover the safety valve of the lithium ion secondary battery cell. It may be in a strip shape, or may be formed into a shape that can A lid that covers the upper part of the lithium-ion secondary battery cell.

When the rubber molded body is in the form of a belt, the belt-shaped rubber molded body can be wound around the lithium ion secondary battery cell in a manner that covers the safety valve, and the ends of the belt-shaped rubber molded body can be attached and fixed with the above-mentioned adhesive tape. .

Alternatively, for example, a strip-shaped rubber molded body may be spirally wound so as to overlap by half a pitch, and its end may be fixed with an adhesive tape to cover substantially the entire outer peripheral surface of the lithium ion secondary battery cell.

It is also possible to form an adhesive layer on at least a part of one side of the rubber molded body, such as the peripheral portion of one side, to adhere and fix the rubber molded body to the lithium ion secondary battery cell.

In each of the above embodiments, the rubber molded body is attached to the outer periphery of the lithium ion secondary battery cell via an insulating sheet. However, as another embodiment of the present invention, the insulating sheet may be omitted.

Each of the above embodiments can be combined appropriately. For example, the sheet-like rubber molded body 6 covering the lithium ion secondary battery cell 1 can be attached with the adhesive tape 8 shown in FIG. 5 above, with the putty-like composition 9 in FIG. Together and fixed in the putty-like composition 9.

In addition, at least part of the outer peripheral surface of the plurality of lithium ion secondary battery cells 1 shown in FIGS. 8 to 10 can also be covered with the putty-like composition 9 shown in FIGS. 6 and 7 . In this case, the space between two adjacent lithium-ion secondary battery cells 1 and 1 may be covered with the putty-like composition 9, or may not be covered with the putty-like composition 9.

In each of the above embodiments, the rubber molding system is attached to cover the safety valve of the lithium ion secondary battery cell, but it may also be attached to cover the exhaust hole instead of the safety valve.

Each of the above embodiments has been described as being applied to a rectangular lithium ion secondary battery cell, but of course the present invention can be similarly applied to a cylindrical lithium ion secondary battery cell. Furthermore, it is suitable for lithium-ion secondary battery cells with high energy density. Specifically, it is suitable for lithium-ion secondary battery cells with energy density of 300 Wh/kg or more, and more preferably 400 Wh/kg or more.

1: Lithium ion secondary battery cell 2:Packaging can 3: Positive terminal 4: Negative terminal 5:Safety valve 6: Rubber molded body 7: Insulation sheet 8: Adhesive tape 9: Putty-like composition 10:Packaging shell 11:Battery pack

[Fig. 1] is a perspective view of a lithium ion secondary battery cell equipped with a rubber molded body according to an embodiment of the present invention. [Fig. 2] is a perspective view showing a rubber molded body and a lithium ion secondary battery cell according to one embodiment of the present invention. [Fig. 3] A perspective view of a lithium ion secondary battery cell with the rubber molded body of Fig. 2 attached. [Fig. 4] is a cross-sectional view along line A-A in Fig. 3. [Fig. 5] is a perspective view corresponding to Fig. 3 of another embodiment of the present invention. [Fig. 6] is a perspective view corresponding to Fig. 3 of another embodiment of the present invention. [Fig. 7] is a cross-sectional view along line B-B in Fig. 6. [Fig. [Fig. 8] is a perspective view corresponding to Fig. 2 of another embodiment of the present invention. [Fig. 9] A perspective view of a lithium ion secondary battery cell with the rubber molded body of Fig. 8 attached. [Fig. 10] is a schematic structural diagram of a battery pack according to an embodiment of the present invention.

1: Lithium ion secondary battery cell

2:Packaging can

3: Positive terminal

4: Negative terminal

5:Safety valve

6: Rubber molded body

7: Insulation sheet

8: Adhesive tape

Claims (9)

A rubber molded body attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole to at least cover the safety valve or the vent hole, utilizing one-way heat flow in accordance with JIS H7903:2008 The thermal conductivity measured by the steady-state comparison method (measurement temperature: 33℃) does not reach 1.0W/m‧K, and the thickness of the part covering the safety valve or the exhaust hole is 0.3mm or more and 10.0mm or less. Based on JIS K6253, The surface hardness measured using an A-type hardness meter is above 50 and below 90. A rubber molded article according to claim 1, wherein the rubber molded article has an elongation at the time of cutting of not less than 80% and not more than 500%. A rubber molded body that is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole to cover at least the safety valve or the vent hole. The rubber molding system uses a silicone rubber composition Formed and hardened, the silicone rubber composition contains 10 to 100 parts by mass of powdered silicon dioxide and 10 to 50 parts by mass of layered silicic acid based on 100 parts by mass of organic polysiloxane. Salt, not less than 0.5 parts by mass and not more than 20 parts by mass of titanium oxide, and not less than 4.0 parts by mass and not more than 14.0 parts by mass of hardener. The rubber molded article of Claim 3, wherein the rubber molded article has an elongation at the time of cutting of 80% or more and 500% or less. A rubber molded body that is attached to the outer periphery of one or more lithium ion secondary battery cells having a safety valve or a vent hole to cover at least the safety valve or the vent hole. The rubber molding system uses a silicone rubber composition Formed and hardened, the silicone rubber composition contains 10 to 100 parts by mass of powdered silicon dioxide and 10 to 50 parts by mass of layered silicic acid based on 100 parts by mass of organic polysiloxane. Salt, 0.5 parts by mass to 20 parts by mass of titanium oxide, and 4.0 parts by mass to 14.0 parts by mass of hardener. The thermal conductivity of the rubber molded article was measured using the one-way heat flow steady-state comparison method in accordance with JIS H7903:2008. The temperature (measurement temperature: 33℃) does not reach 1.0W/m‧K. The thickness of the rubber molded body covering the safety valve or the exhaust hole is 0.3 mm or more and 10.0 mm or less. The rubber molded body is based on JIS K6253. The surface hardness measured using an A-type hardness meter is above 50 and below 90. The rubber molded article of claim 5, wherein the rubber molded article has an elongation at the time of cutting of not less than 80% and not more than 500%. The rubber molded body according to any one of claims 1 to 6, wherein the rubber molded body is in the shape of a sheet, a belt, or a cover. A battery pack including one or more lithium ion secondary battery cells attached to the outer periphery of the rubber molded body according to any one of claims 1 to 7. The battery pack of claim 8, wherein at least part of the outer peripheral surface of the lithium ion secondary battery cell is covered with a putty-like composition having thermal conductivity.

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